bill owen to the rescue....http://www.youtube.com/watch?v=7wGlWZ24QsE&feature=player_embedded
this way is quick and easy, but the bit costs like $40. i've modded my case using this and had no problems, not sure how well it cuts steel, but it eats up aluminum just fine.
you can also use a dremmel and have really steady hands.
good luck and happy modding

Great vid. It's always good to have tools; not against buying a hole saw like that. Thanks for sharing! +1 rep.